Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Ordinary Shares Ionis Share Purchase Agreement	Ordinary Shares	Additional Paid-in Capital Ionis Share Purchase Agreement	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Ionis Share Purchase Agreement	Total
Beginning balance at Dec. 31, 2020		$ 266		$ 249,947	$ (3,193)	$ (151,560)		$ 95,460
Beginning balance (in shares) at Dec. 31, 2020		21,094,557
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 10		7,173				7,183
Issuance of ADSs upon exercise of share options (in shares)		703,786
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses	$ 4	$ 104	$ 7,554	290,880			$ 7,558	290,984
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses (in shares)	282,485	7,498,536
Share-based compensation expense				12,083				12,083
Foreign currency translation adjustment					(195)			(195)
Net Income (Loss)						(66,819)		(66,819)
Ending balance at Dec. 31, 2021		$ 384		567,637	(3,388)	(218,379)		346,254
Ending balance (in shares) at Dec. 31, 2021		29,579,364
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 1		988				989
Issuance of ADSs upon exercise of share options (in shares)		78,074
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses		$ 2		5,701				5,703
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses (in shares)		181,455
Issuance of ADSs upon vesting of restricted share units (in shares)		35,000
Share-based compensation expense				26,779				26,779
Foreign currency translation adjustment					3,775			3,775
Net Income (Loss)						(112,717)		(112,717)
Ending balance at Dec. 31, 2022		$ 387		601,105	387	(331,096)		$ 270,783
Ending balance (in shares) at Dec. 31, 2022		29,873,893						29,873,893
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options				681				$ 681
Issuance of ADSs upon exercise of share options (in shares)		54,023
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses		$ 162		249,183				249,345
Issuance of ADSs and non-voting ordinary shares, net of commissions and offering expenses (in shares)		12,384,706
Issuance of ADSs upon vesting of restricted share units		$ 1						1
Issuance of ADSs upon vesting of restricted share units (in shares)		119,144
Share-based compensation expense				32,477				32,477
Foreign currency translation adjustment					(1,691)			(1,691)
Net Income (Loss)						(180,664)		(180,664)
Ending balance at Dec. 31, 2023		$ 550		$ 883,446	$ (1,304)	$ (511,760)		$ 370,932
Ending balance (in shares) at Dec. 31, 2023		42,431,766						42,431,766